[0001] This application is based on Japanese Patent Application Serial No.
2011-230311 filed with the Japan Patent Office on October 20, 2011, Japanese Patent Application
Serial No.
2011-230312 filed with the Japan Patent Office on October 20, 2011, Japanese Patent Application
Serial No.
2012-219338 filed with the Japan Patent Office on October 1, 2012 and Japanese Patent Application
Serial No.
2012-219339 filed with the Japan Patent Office on October 1, 2012.
Background
[0002] The present disclosure relates to a differential transformer type magnetic sensor
using planar coils.
[0003] In an image forming apparatus using a toner as a developer, a magnetic sensor is
used to detect the remaining amount and density of the toner. There are various types
of magnetic sensors. A differential transformer type magnetic sensor is so configured
that a drive coil, a differential coil which functions as a detection coil and a differential
coil which functions as a reference coil are arranged on the same core.
[0004] A differential transformer type magnetic sensor in which a first coil (drive coil),
a second coil (differential coil), a third coil (differential coil) and a fourth coil
(drive coil) are respectively arranged on first, second, third and fourth layers and
insulating substrates are arranged between the respective layers has been proposed
as an example.
[0005] A differential transformer type magnetic sensor in which a first coil (drive coil)
and a third coil (differential coil) are arranged side by side on one surface of an
insulating magnetic substrate and a second coil (drive coil) and a fourth coil (differential
coil) are arranged side by side on the other surface of the insulating magnetic substrate
has been proposed as another example.
[0006] Since the first to fourth coils are arranged one over another via the substrates
in the one example of the differential transformer type magnetic sensor, a distance
between the first coil (drive coil) and the second coil (differential coil) and that
between the third coil (differential coil) and the fourth coil (drive coil) can be
approximated to each other. Thus, magnetic coupling between the first and second coils
and that between the third and fourth coils can be increased. Therefore, a highly
accurate magnetic sensor can be realized. However, four layers of substrates are necessary,
which constitutes an obstacle to the miniaturization of the magnetic sensor and increases
the production cost of the magnetic sensor.
[0007] Since two layers (both surfaces) of substrates are used in the other example of the
differential transformer type magnetic sensor, the production cost of the magnetic
sensor can be reduced. However, the first coil (drive coil) and the third coil (differential
coil) are arranged side by side on the one surface of the substrate and the second
coil (drive coil) and the fourth coil (differential coil) are arranged side by side
on the other side of the substrate. The first and third coils are not facing each
other, and the second and fourth coils are not facing each other. Thus, magnetic coupling
between the first and third coils and that between the second and fourth coils cannot
be increased. Therefore, a highly accurate magnetic sensor cannot be realized.
[0008] Further, a differential transformer type magnetic sensor necessitates a zero adjustment,
i.e. an adjustment to balance between an electromotive force generated in one differential
coil (detection coil) and that generated in the other differential coil (reference
coil). The zero adjustment can be made by providing the magnetic sensor with a mechanism
for adjusting the position of a core of a differential transformer and by adjusting
the position of the core. However, in the case of a differential transformer using
planar coils patterned on a printed circuit board as a drive coil and differential
coils, it is difficult to provide the above mechanism on the printed circuit board.
[0009] The publication of
CHOI S O et al.: "An integrated micro fluxgate magnetic sensor", SENSORS AND ACTUATORS
A, ELSEVIER SEQUOIA S.A., LAUSANNE, CH, vol. 55, no. 2, 31 July 1996, pages 121-126,
ISSN: 0924-4247, DOI: 10.1016/S0924-4247(97)80066-0 relates to an integrated fluxgate magnetic sensor with planar fluxgate sensing elements
and on-chip sensor interface circuits based on silicon integration technology. A flux
gate sensor and its manufactoring method is also disclosed in
JP 2001 099654 A.
[0011] A problem of the present invention is to provide a highly accurate differential transformer
type magnetic sensor while realizing a configuration using planar coils arranged on
a substrate as a drive coil and differential coils.
[0012] This problem is solved by the subject-matter of appended independent claim 1. Preferred
embodiments are subject to the appended dependent claims.
Summary
[0013] A differential transformer type magnetic sensor according to one aspect of the present
disclosure includes a substrate, a drive coil, a first differential coil, a second
differential coil and a first selector unit. The drive coil includes a planar coil
arranged on the substrate. The first differential coil includes a planar coil arranged
on the substrate and generates an electromotive force when the drive coil is driven.
The second differential coil includes a planar coil arranged on the substrate and
is connected to the first differential coil and configured to generate an electromotive
force when the drive coil is driven. The first selector unit is used for a zero adjustment
of a differential transformer formed by the drive coil, the first differential coil
and the second differential coil. The first differential coil includes a plurality
of first branch lines formed by branching a wire material forming the outermost turn
of the first differential coil. The plurality of first branch lines are so arranged
that the amount of magnetic fluxes passing along the plurality of respective first
branch lines differ when the drive coil is driven. The first selector unit is capable
of selecting any one of the plurality of first branch lines and arranged on the substrate.
[0014] A differential transformer type magnetic sensor according to another aspect of the
present disclosure includes a substrate, a drive coil, a first differential coil and
a second differential coil. The drive coil includes a planar coil arranged on the
substrate. The first differential coil includes a planar coil arranged on the substrate
and generates an electromotive force when the drive coil is driven. The second differential
coil includes a planar coil arranged on the substrate and is connected to the first
differential coil and configured to generate an electromotive force when the drive
coil is driven. The amount of magnetic flux passing along the wire material forming
the outermost turn of the first differential coil and the amount of magnetic flux
passing along the wire material forming the outermost turn of the second differential
coil differ when the drive coil is driven.
[0015] A differential transformer type magnetic sensor according to still another aspect
of the present disclosure includes a substrate, a first drive coil, a first differential
coil, a second drive coil, a first connecting member, a second differential coil,
a second connecting member, a third connecting member and a connection pattern. The
substrate has a first surface and a second surface located on a side opposite to the
first surface. The first drive coil includes a planar coil arranged on the first surface.
The first differential coil includes a planar coil wound in the same direction as
the first drive coil and arranged on the first surface and generates an electromotive
force when the first drive coil is driven. The second drive coil includes a planar
coil wound in a direction opposite to the first drive coil when viewed from the first
surface side and arranged on the second surface. The first connecting member penetrates
through the substrate and connects one end of the first drive coil and one end of
the second drive coil. The second differential coil includes a planar coil wound in
a direction opposite to the second drive coil and arranged on the second surface and
generates an electromotive force when the second drive coil is driven. The second
connecting member penetrates through the substrate and connects one end of the first
differential coil and one end of the second differential coil. The third connecting
member is formed to penetrate through the substrate. The connection pattern is arranged
on the first surface and constitutes a part of the second drive coil or a part of
the second differential coil. A wire material forming the first drive coil and that
forming the first differential coil are alternately arranged on the first surface.
A wire material forming the second drive coil and that forming the second differential
coil are alternately arranged on the second surface. The connection pattern is connected
to the wire material forming the second drive coil or that forming the second differential
coil by the third connecting member, whereby the wire material forming the second
differential coil and that forming the second drive coil are sterically intersected.
[0016] These and other objects, features and advantages of the present disclosure will become
more apparent upon reading the following detailed description along with the accompanying
drawings.
Brief Description of the Drawings
[0017]
FIG. 1 is a schematic diagram showing the internal structure of an image forming apparatus
to which a differential transformer type magnetic sensor according to one embodiment
of the present disclosure can be applied,
FIG. 2 is a block diagram showing the configuration of the image forming apparatus
shown in FIG. 1,
FIG. 3 is a diagram showing an example of a circuit diagram of the differential transformer
type magnetic sensor according to the embodiment,
FIG. 4 is a plan view showing a first surface of an example of a substrate on which
the differential transformer type magnetic sensor according to the embodiment is to
be formed,
FIG. 5 is a plan view showing a second surface of the example of the substrate on
which the differential transformer type magnetic sensor according to the embodiment
is to be formed,
FIG. 6 is a plan view showing a layout example of a first drive coil, a first differential
coil and connection patterns,
FIG. 7 is a plan view showing a state where the first drive coil is extracted from
the first drive coil, the first differential coil and the connection patterns shown
in FIG. 6,
FIG. 8 is a plan view showing a state where the first differential coil is extracted
from the first drive coil, the first differential coil and the connection patterns
shown in FIG. 6,
FIG. 9 is a plan view showing a state where the connection patterns are extracted
from the first drive coil, the first differential coil and the connection patterns
shown in FIG. 6,
FIG. 10 is a plan view showing a layout example of a second drive coil and a second
differential coil,
FIG. 11 is a plan view showing a state where the second drive coil is extracted from
the second drive coil and the second differential coil shown in FIG. 10,
FIG. 12 is a plan view showing a state where the second differential coil is extracted
from the second drive coil and the second differential coil shown in FIG. 10,
FIG. 13 is a perspective view showing coils arranged in a first outer area and a second
outer area,
FIG. 14 is a perspective view showing coils arranged in a first inner area and a second
inner area,
FIG. 15 is a diagram showing an example of a relationship between first branch lines
and magnetic field lines,
FIG. 16 is a perspective view showing the substrate near a selector unit area shown
in FIG. 4, and
FIG. 17 is a sectional view of a substrate formed with a differential transformer
type magnetic sensor according to a modification of the embodiment.
Detailed Description
[0018] Hereinafter, an embodiment of the present disclosure is described in detail based
on the drawings. FIG. 1 is a schematic diagram showing the internal structure of an
image forming apparatus 1 to which a differential transformer type magnetic sensor
according to one embodiment of the present disclosure can be applied. The image forming
apparatus 1 can be applied, for example, to a digital complex machine with functions
of a copier, a printer, a scanner and a facsimile machine. The image forming apparatus
1 includes an apparatus main body 100, a document reading unit 200 and a document
feeding unit 300.
[0019] The document reading unit 200 is arranged atop the apparatus main body 100 and the
document feeding unit 300 is arranged atop the document reading unit 200.
[0020] The document feeding unit 300 functions as an automatic document feeder and is capable
of successively feeding a plurality of documents placed on a document placing portion
301 to the document reading unit 200.
[0021] The document reading unit 200 includes a carriage carrying an exposure lamp and the
like, a document platen made of a transparent member such as a glass, a CCD (Charge
Coupled Device) sensor and document reading slits (any of them is not shown). The
CCD sensor outputs information of a read document as image data.
[0022] The apparatus main body 100 includes a sheet storage unit 101, an image forming station
103 and a fixing unit 105. The sheet storage unit 101 is arranged in a lowest part
of the apparatus main body 100 and includes a plurality of sheet cassettes capable
of storing a stack of sheets. Only the uppermost sheet cassette 107a is shown in FIG.
1.
[0023] The uppermost sheet in the sheet stack stored in the cassette selected out of a plurality
of sheet cassettes including the sheet cassette 107a is fed toward a sheet conveyance
path 107 of the apparatus main body 100 by driving a pickup roller (not shown). The
sheet is conveyed to the image forming station 103 through the sheet conveyance path
107.
[0024] The sheet conveyance path 107 extends upward substantially in a vertical direction
along one side surface (right side surface in FIG. 1) of the apparatus main body 100
and is curved to extend substantially in a horizontal direction along and below the
document reading unit 200 toward the other side surface (left side surface in FIG.
1) in an upper part. A discharge tray 131 is provided at an end part of the sheet
conveyance path 107.
[0025] The image forming station 103 forms a toner image on a sheet conveyed thereto. The
image forming station 103 includes a yellow image forming unit 111Y, a magenta image
forming unit 111M, a cyan image forming unit 111C and a black image forming unit 111BK
arranged in accordance with an order of transferring a toner image to a transfer belt
113. These units have a similar configuration and are, hence, described, taking the
yellow image forming unit 111Y as an example.
[0026] The yellow image forming unit 111Y includes a photoconductive drum 115 and an exposure
device 117. A charging device 119, a developing device 121 and a cleaning device 123
are arranged around the photoconductive drum 115. A two-component developer which
is mixed by yellow toners and carriers is contained in the developing device 121.
The charging device 119 uniformly charges the circumferential surface of the photoconductive
drum 115. The exposure device 117 generates a beam modulated to correspond to image
data (image data output from the document reading unit 200, image data transmitted
from a personal computer, facsimile-received image data or the like) and irradiates
the generated beam to the uniformly charged circumferential surface of the photoconductive
drum 115. This causes an electrostatic latent image corresponding to yellow image
data to be formed on the circumferential surface of the photoconductive drum 115.
By supplying a yellow toner from the developing device 121 to the circumferential
surface of the photoconductive drum 115 in this state, a toner image corresponding
to the yellow image data is formed on the circumferential surface.
[0027] The transfer belt 113 can move counterclockwise while being sandwiched between the
photoconductive drum 115 and a primary transfer roller 125. The yellow toner image
is transferred from the photoconductive drum 115 to the transfer belt 113. The yellow
toner remaining on the circumferential surface of the photoconductive drum 115 is
removed by the cleaning device 123. The above is the description of the yellow image
forming unit 111Y.
[0028] Containers containing toners of corresponding colors, i.e. a yellow toner container
127Y, a magenta toner container 127M, a cyan toner container 127C and a black toner
container 127BK are arranged above the yellow image forming unit 111Y, the magenta
image forming unit 111M, the cyan image forming unit 111C and the black image forming
unit 111BK. The toners are supplied to the developing devices 121 of the respective
colors from the corresponding containers.
[0029] As described above, a yellow toner image is transferred to the transfer belt 113,
a magenta toner image is transferred onto this toner image, and a cyan toner image
and a black toner image are similarly transferred in a superimposition manner. This
causes a full-color toner image to be formed on the transfer belt 113. By transferring
the toner images of the respective color patterns in a superimposition manner in this
way, the full-color toner image is formed on the transfer belt 113. The full-color
toner image is transferred to a sheet conveyed from the sheet storage unit 101 described
above by a secondary transfer roller 129.
[0030] The sheet having the color toner image transferred thereto is fed to the fixing unit
105. The fixing unit 105 includes a heating roller and a fixing roller. The sheet
having the full-color toner image transferred thereto is sandwiched by these rollers.
This causes heat and pressure to be applied to the full-color toner image and the
sheet to fix the full-color toner image to the sheet. The sheet is discharged to the
discharge tray 131.
[0031] FIG. 2 is a block diagram showing the configuration of the image forming apparatus
1 shown in FIG. 1. The image forming apparatus 1 is so configured that the apparatus
main body 100, a differential transformer type magnetic sensor 3, the toner containers
127Y, 127M, 127C and 127BK, the document reading unit 200, the document feeding unit
300, an operation unit 400, a control unit 500 and a communication unit 600 are connected
to each other by a bus. Since the apparatus main body 100, the toner containers 127Y,
127M, 127C and 127BK, the document reading unit 200 and the document feeding unit
300 are already described, they are not described.
[0032] The differential transformer type magnetic sensor 3 is used to measure a toner/carrier
mixing ratio in the developing device 121. That is, in a two-component development
method, the ratio of the carrier (magnetic substance) increases in the developing
device 121 as the toner (nonmagnetic substance) decreases. This causes an increase
in the amount of the magnetic substance in a unit volume near a detection surface
of the differential transformer type magnetic sensor 3. On the other hand, in the
developing device 121, the ratio of the carrier decreases when the toner increases.
This causes a decrease in the amount of the magnetic substance in a unit volume near
the detection surface of the differential transformer type magnetic sensor 3. By detecting
this change in the amount of the magnetic substance by the differential transformer
type magnetic sensor 3, the toner/carrier mixing ratio in the developing device 121
is controlled. The differential transformer type magnetic sensor 3 is described in
detail later.
[0033] Note that although the two-component development method is described in this embodiment,
the differential transformer type magnetic sensor 3 is usable also in a one-component
development method using a toner containing a magnetic substance. In this case, the
remaining amount of the magnetic toner in the developing device or the toner container
is measured by mounting the differential transformer type magnetic sensor 3 in the
developing device or the toner container.
[0034] The operation unit 400 includes an operation key unit 401 and a display unit 403.
The display unit 403 has a touch panel function and displays a screen including soft
keys. A user performs settings necessary to perform functions such as a copy function
by operating the soft keys while viewing the screen.
[0035] The operation unit 401 includes operation keys composed of hard keys. Specifically,
a start key, a numerical keypad, a stop key, a reset key, function changeover keys
to switch copy, printer, scanner and facsimile machine functions and the like are
provided.
[0036] The start key is a key for starting an operation such as a copying operation or facsimile
transmission. The numerical keypad includes keys used to input a number such as the
number of sets to be copied or a facsimile number. The stop key is a key for stopping
a copying operation or the like halfway. The reset key is a key for returning a set
content to a default state.
[0037] The function changeover keys include a copy key, a transmit key and the like and
switch a copy function, a transmit function and the like from one to another. If the
copy key is operated, an initial screen for copy is displayed on the display unit
403. If the transmit key is operated, an initial screen for facsimile transmission
and mail transmission is displayed on the display unit 403.
[0038] The control unit 500 includes a CPU (Central Processing Unit), a ROM (Read Only Memory),
a RAM (Random Access Memory), an image memory and the like. The CPU performs a control
necessary to operate the image forming apparatus 1 on the above constituent elements
of the image forming apparatus such as the apparatus main body 100. The ROM stores
software necessary to control the operation of the image forming apparatus 1. The
RAM is used to temporarily store data generated when the software is implemented and
store application software and the like. The image memory temporarily stores image
data (image data output from the document reading unit 200, image data transmitted
from a personal computer, facsimile-received image data or the like).
[0039] The communication unit 600 includes a facsimile communication unit 601 and a network
I/F unit 603. The facsimile communication unit 601 includes an NCU (Network Control
Unit) for controlling a telephone line connection to a destination facsimile machine
and a modulation/demodulation circuit for modulating and demodulating a signal for
facsimile communication. The facsimile communication unit 601 is connected to a telephone
line 605.
[0040] The network I/F unit 603 is connected to a LAN (Local Area Network) 607. The network
I/F unit 603 is a communication interface circuit for carrying out a communication
with terminal units such as personal computers connected to the LAN 607.
[0041] FIG. 3 is a diagram showing an example of a circuit diagram of the differential transformer
type magnetic sensor 3 (hereinafter, may be written as "magnetic sensor 3" in some
cases) according to one embodiment of the present disclosure. The differential transformer
type magnetic sensor 3 includes a first drive coil 4, a second drive coil 5, a first
differential coil 6, a second differential coil 7, an oscillator circuit 11, an amplifier
circuit 12, a resistor 13 and a capacitor 14.
[0042] The oscillator circuit 11 generates a high-frequency current for driving the first
and second drive coils 4, 5. The first and second drive coils 4, 5 are connected in
series. One end of the first drive coil 4 and one end of the second drive coil 5 are
so connected that a magnetic flux generated by the first drive coil 4 and that generated
by the second drive coil 5 flow in the same direction when a high-frequency current
flows in the first and second drive coils 4, 5. This prevents the magnetic flux generated
by the first drive coil 4 and that generated by the second drive coil 5 from being
canceled out. The other end of the first drive coil 4 and the other end of the second
drive coil 5 are connected to the oscillator circuit 11.
[0043] The first differential coil 6 is magnetically coupled to the first drive coil 4.
The second differential coil 7 is magnetically coupled to the second drive coil 5.
The first and second differential coils 6, 7 are connected in series. One end of the
first differential coil 6 and one end of the second differential coil 7 are so connected
that a magnetic flux generated by the first differential coil 6 and that generated
by the second differential coil 7 flow in opposite directions when an induction current
flows in the first differential coil 6 and the second differential coil 7. This causes
a differential voltage V0 (= electromotive force V1 of the first differential coil
6 - electromotive force V2 of the second differential coil 7) to be input to the amplifier
circuit 12.
[0044] The other end of the first differential coil 6 is connected to the amplifier circuit
12 via the resistor 13 and the other end of the second differential coil 7 is connected
thereto via the capacitor 14. The resistor 13 is connected to a base of a bipolar
transistor (not shown) in the amplifier circuit 12 and used to set an amplification
factor of the amplifier circuit 12.
[0045] The capacitor 14 has a function of cutting a direct-current component out of the
differential voltage V0. This causes only an alternating-current component of the
differential voltage V0 to be input to the amplifier circuit 12.
[0046] The resistor 13 is mounted at any one of positions P1 to P5. The capacitor 14 is
mounted at any one of positions P6 to P10. A part for adjusting the mounted position
of the resistor 13 is called a first selector unit 15. A part for adjusting the mounted
position of the capacitor 14 is called a second selector unit 16. A zero adjustment
of a differential transformer of the magnetic sensor 3 is made by adjusting the mounted
position of the resistor 13 and the mounted position of the capacitor 14. This is
described later. The differential transformer is formed by the first drive coil 4,
the second drive coil 5, the first differential coil 6 and the second differential
coil 7.
[0047] The operation of the magnetic sensor 3 is briefly described. When a high-frequency
current generated in the oscillator circuit 11 flows into the first and second drive
coils 4, 5, an electromotive force V1 is generated in the first differential coil
6 and an electromotive force V2 is generated in the second differential coil 7. The
first differential coil 6 has a function of a reference coil and the second differential
coil 7 has a function of a detection coil. If the ratio of the magnetic substance
(carrier) increases near the second differential coil 7, the electromotive force V2
becomes larger than the electromotive force V1, wherefore the differential voltage
V0 does not become 0 V. The differential voltage V0 is amplified in the amplifier
circuit 12 and a toner/carrier mixing ratio (toner remaining amount in the one-component
development method) is detected using a signal output from the amplifier circuit 12.
[0048] Next, the configuration of the differential transformer type magnetic sensor 3 according
to this embodiment is described in detail. FIG. 4 is a plan view showing a first surface
31 of an example of a substrate 21 on which the magnetic sensor 3 is to be formed.
FIG. 5 is a plan view showing a second surface 41 of the example of the substrate
21 on which the magnetic sensor 3 is to be formed. FIG. 5 shows a state when the second
surface 41 is viewed through the substrate 21 from the first surface 31 side. The
substrate 21 is an insulating single-layer printed circuit board and has the first
surface 31 and the second surface 41 located on a side opposite to the first surface
31.
[0049] The substrate 21 has a shape obtained by cutting off a part including one corner
of a rectangle from the rectangle. The substrate 21 is divided into a part 21a having
a constant vertical dimension, a part 21b continuous with the part 21a and having
a gradually decreasing vertical dimension and a part 21c having a constant vertical
dimension. Coils and the like of the magnetic sensor 3 are arranged on the parts 21a,
21b as described next. Various circuits (oscillator circuit 22, amplifier circuit
12, etc.) of the magnetic sensor 3 are arranged on the part 21c.
[0050] With reference to FIGS. 3 and 4, the first surface 31 has a first inner area 32,
a first outer area 33 and a selector unit area 34. These areas are located on the
parts 21a, 21b of the substrate 21. The first differential coil 6 is arranged in the
first inner area 32. The first outer area 33 surrounds the first inner area 32. The
first differential coil 6 and the first drive coil 4 are arranged in the first outer
area 33. The selector unit area 34 is adjacent to a part of the first outer area 33.
The first and second selector units 15, 16 for adjusting a zero point of the differential
transformer of the magnetic sensor 3 are arranged in the selector unit area 34.
[0051] With reference to FIGS. 3 and 5, the second surface 41 has a second inner area 42
and a second outer area 43. These areas are located on the parts 21a, 21b of the substrate
21. The second differential coil 7 is arranged in the second inner area 42. The second
outer area 43 surrounds the second inner area 42. The second differential coil 7 and
the second drive coil 5 are arranged in the second outer area 43.
[0052] FIG. 6 is a plan view showing a layout example of the first drive coil 4, the first
differential coil 6 and connection patterns 10a, 10b, 10c, 10d, 10e, 10f and 10g.
The first drive coil 4, the first differential coil 6 and the connection patterns
10a to 10g are arranged on the first surface 31 of the substrate 21. Since the first
differential coil 6 functions as the reference coil, the first surface 31 can be called
a reference coil surface.
[0053] First, the first drive coil 4 is described. FIG. 7 is a plan view showing a state
where the first drive coil 4 is extracted from the first drive coil 4, the first differential
coil 6 and the connection patterns 10a to 10g shown in FIG. 6. With reference to FIGS.
4 and 7, the first drive coil 4 includes a planar coil arranged in the first outer
area 33. Specifically, the first drive coil 4 is made of a wire material 4a wound
in an octagonal shape, and the wire member 4a is so patterned that the octagonal shape
becomes gradually larger in a counterclockwise direction from a terminal 4b as a start
end.
[0054] Next, the first differential coil 6 is described. FIG. 8 is a plan view showing a
state where the first differential coil 6 is extracted from the first drive coil 4,
the first differential coil 6 and the connection patterns 10a to 10g shown in FIG.
6. With reference to FIGS. 4 and 8, the first differential coil 6 includes a planar
coil wound in the same direction as the first drive coil 4 and arranged in the first
inner area 32 and the first outer area 33. Specifically, the first differential coil
6 is made of a wire material 6a wound in an octagonal shape, and the wire member 6a
is so patterned that the octagonal shape becomes gradually larger in the counterclockwise
direction from a terminal 6b as a start end.
[0055] With reference to FIGS. 4 and 6, the wire member forming the first differential coil
6 and that forming the first drive coil 4 are alternately arranged in the first outer
area 33. The first differential coil 6 includes five (an example of plural) first
branch lines 6c1, 6c2, 6c3, 6c4 and 6c5 formed by branching the wire member forming
the outermost turn of the first drive coil 6. The first branch lines 6c1 to 6c5 are
written as first branch lines 6c in some cases unless it is necessary to distinguish
the first branch lines 6c1 to 6c5. The five first branch lines 6c are so arranged
that the amounts of magnetic fluxes passing along the respective first branch lines
6c differ when the first drive coil 4 is driven. The first branch lines 6c are described
in detail later.
[0056] FIG. 9 is a plan view showing a state where the connection patterns 10a to 10g are
extracted from the first drive coil 4, the first differential coil 6 and the connection
patterns 10a to 10g shown in FIG. 6. The connection patterns 10a to 10g are used for
connection with the wire material forming the second differential coil 7. The connection
patterns 10a to 10g are described later together with the second differential coil
7.
[0057] FIG. 10 is a plan view showing a layout example of the second drive coil 5 and the
second differential coil 7. FIG. 10 shows a state when the second surface 41 is viewed
through the substrate 21 from the first surface 31 side shown in FIG. 6. The second
drive coil 5 and the differential coil 7 are arranged on the second surface 41 of
the substrate 21. Since the second differential coil 7 functions as the detection
coil, the second surface 41 can be called a detection coil surface.
[0058] First, the second drive coil 5 is described. FIG. 11 is a plan view showing a state
where the second drive coil 5 is extracted from the second drive coil 5 and the second
differential coil 7 shown in FIG. 10. With reference to FIGS. 5 and 11, the second
drive coil 5 includes a planar coil wound in a direction opposite to the first drive
coil 4 (FIG. 7) when viewed from the first surface 31 side and arranged in the second
outer area 43. Specifically, the second drive coil 5 is made of a wire material 5a
wound in an octagonal shape, and the wire member 5a is so patterned that the octagonal
shape becomes gradually larger in a clockwise direction from a terminal 5b as a start
end.
[0059] The second drive coil 5 is connected to the first drive coil 4. This is described
with reference to FIG. 13. FIG. 13 is a perspective view showing the coils arranged
in the first outer area 33 and the second outer area 43. A first connecting member
51 is electrically conductive and embedded in a through hole (not shown) formed in
the substrate 21. The terminal 4b as one end of the first drive coil 4 and the terminal
5b as one end of the second drive coil 5 are connected by the first connecting member
51.
[0060] Next, the second differential coil 7 is described. FIG. 12 is a plan view showing
a state where the second differential coil 7 is extracted from the second drive coil
5 and the second differential coil 7 shown in FIG. 10. With reference to FIGS. 5 and
12, the second differential coil 7 includes a planar coil wound in a direction opposite
to the second drive coil 5 (FIG. 11) and arranged in the second inner area 42 and
the second outer area 43. Specifically, the second differential coil 7 is made of
a wire material 7a wound in an octagonal shape, and the wire member 7a is so patterned
that the octagonal shape becomes gradually larger in the counterclockwise direction
from a terminal 7b as a start end.
[0061] The second differential coil 7 is connected to the first differential coil 6. This
is described with reference to FIG. 14. FIG. 14 is a perspective view showing the
coils arranged in the first inner area 32 and the second inner area 42. A second connecting
member 52 is electrically conductive and embedded in a through hole (not shown) formed
in the substrate 21. The terminal 6b as one end of the first differential coil 6 and
the terminal 7b as one end of the second differential coil 7 are connected by the
second connecting member 52.
[0062] With reference to FIG. 12, the second differential coil 7 includes five (an example
of plural) second branch lines 7c1, 7c2, 7c3, 7c4 and 7c5 formed by branching the
wire member forming the outermost turn of the second drive coil 7. The second branch
lines 7c1 to 7c5 are written as second branch lines 7c in some cases unless it is
necessary to distinguish the second branch lines 7c1 to 7c5. The five second branch
lines 7c are so arranged that the amounts of magnetic fluxes passing along the respective
second branch lines 7c differ when the second drive coil 5 is driven. The second branch
lines 7c are described in detail later.
[0063] With reference to FIGS. 6 and 10, the width of the wire material of the first drive
coil 4, that of the wire material of the second drive coil 5, that of the wire material
of the first differential coil 6, that of the wire material of the second differential
coil 7 and those of the respective connection patterns 10a to 10g are, for example,
0.15 mm. An interval between the adjacent wire materials is, for example, 0. 15 mm.
External dimensions of the first and second differential coils 6, 7 are, for example,
24.0 mm. External dimensions of the first and second drive coils 4, 5 are, for example,
23.4 mm.
[0064] To improve measurement accuracy of the magnetic sensor 3, the differential voltage
V0 needs to be largely changed in an output range (e.g. 0.2 to 3.3 V) of the differential
voltage V0. To this end, the electromotive force V1 generated by the first differential
coil 6 and the electromotive force V2 generated by the second differential coil 7
are preferably balanced in a state where no magnetic substance is present near the
magnetic sensor 3. The following arrangement is made to balance the electromotive
forces V1 and V2. A turn number of the first differential coil 6 and that of the second
differential coil 7 are made equal. The first differential coil 6 is arranged on the
first surface 31 and the second differential coil 7 is arranged on the second surface
41 such that the pattern of the first differential coil 6 and that of the second differential
coil 7 maximally overlap via the substrate 21. Similarly, a turn number of the first
drive coil 4 and that of the second drive coil 5 are made equal (e.g. a turn number
of 7) . The first drive coil 4 is arranged on the first surface 31 and the second
drive coil 5 is arranged on the second surface 41 such that the pattern of the first
drive coil 4 and that of the second drive coil 5 maximally overlap via the substrate
21.
[0065] With reference to FIGS. 5 and 10, the wire material forming the second differential
coil 7 and that forming the second drive coil 5 are alternately arranged in the second
outer area 43. The second drive coil 5 is wound clockwise with the terminal 5b as
the start end. The second differential coil 7 is wound counterclockwise with the terminal
7b as the start end. Since the second differential coil 7 is wound in a direction
opposite to the second drive coil 5, the second differential coil 7 and the second
drive coil 5 intersect in the second outer area 43. To prevent the contact of the
second differential coil 7 and the second drive coil 5, the second differential coil
7 and the second drive coil 5 are sterically intersected using the connection patterns
10a to 10g shown in FIG. 9. This steric intersection is described.
[0066] With reference to FIG. 12, the second differential coil 7 is wound counterclockwise
with the terminal 7b as the start end and reaches a terminal 7d1. The second outer
area 43 starts from the terminal 7d1. The second differential coil 7 has a pattern
in which a part of the wire material is missing in each turn of the second differential
coil 7 in the second outer area 43. In this pattern, the first turn of the second
differential coil 7 starts at a terminal 7d2 and ends at a terminal 7d3, the second
turn of the second differential coil 7 starts at a terminal 7d4 and ends at a terminal
7d5, the third turn of the second differential coil 7 starts at a terminal 7d6 and
ends at a terminal 7d7, the fourth turn of the second differential coil 7 starts at
a terminal 7d8 and ends at a terminal 7d9, the fifth turn of the second differential
coil 7 starts at a terminal 7d10 and ends at a terminal 7d11, the sixth turn of the
second differential coil 7 starts at a terminal 7d12 and ends at a terminal 7d13 and
the seventh turn of the second differential coil 7 starts at a terminal 7d14 and reaches
the five second branch lines 7c.
[0067] With reference to FIGS. 9 and 10, the terminals 7d1 and 7d2 are connected to the
connection pattern 10a. The terminals 7d3 and 7d4 are connected to the connection
pattern 10b. The terminals 7d5 and 7d6 are connected to the connection pattern 10c.
The terminals 7d7 and 7d8 are connected to the connection pattern 10d. The terminals
7d9 and 7d10 are connected to the connection pattern 10e. The terminals 7d11 and 7d12
are connected to the connection pattern 10f. The terminals 7d13 and 7d14 are connected
to the connection pattern 10g. The connection patterns 10a to 10g constitute parts
of the second differential coil 7. The connection patterns 10a to 10g are arranged
in the second outer area 33 at positions where they sterically intersect with the
wire material forming the second drive coil 5.
[0068] Third connecting members are used to connect these pairs of terminals (e.g. terminals
7d1 and 7d2) and the connection patterns 10a to 10g. With reference to FIG. 13, the
third connecting members 53a, 53b, 53c and 53d are electrically conductive and embedded
in through holes (not shown) formed in the substrate 21. The terminal 7d1 and one
end of the connection pattern 10a are connected by the third connecting member 53a.
The other end of the connection pattern 10a and the terminal 7d2 are connected by
the third connecting member 53b. The terminal 7d3 and one end of the connection pattern
10b are connected by the third connecting member 53c. The other end of the connection
pattern 10b and the terminal 7d4 are connected by the third connecting member 53d.
Although not shown, the remaining terminals 7d5 to 7d14 and the remaining connection
patterns 10c to 10g are connected in a similar manner. The above is the description
of the steric intersection of the second differential coil 7 and the second drive
coil 5.
[0069] As described above, the five first branch lines 6c shown in FIG. 6 are so arranged
that the amounts of magnetic fluxes passing along the respective first branch lines
6c differ when the first drive coil 4 is driven. The five second branch lines 7c shown
in FIG. 10 are so arranged that the amounts of magnetic fluxes passing along the respective
second branch lines 7c differ when the second drive coil 5 is driven. Since the first
branch lines 6c and the second branch lines 7c are arranged in the same way, description
is made using the first branch lines 6c.
[0070] With reference to FIGS. 6 and 8, the first differential coil 6 and the first drive
coil 4 are wound in the octagonal shape. The first branch lines 6c1, 6c2 and 6c3 are
arranged along two consecutive sides of the octagonal shape on the outermost turn
of the first drive coil 4. The first branch lines, 6c4 and 6c5 are arranged along
the first one of the above two sides. The first branch line 6c2 is arranged at the
outer side of the first branch line 6c1, the first branch line 6c3 is arranged at
the outer side of the first branch line 6c2, the first branch line 6c4 is arranged
at the outer side of the first branch line 6c3, and the first branch line 6c5 is arranged
at the outer side of the first branch line 6c4. Lengths of the five first branch lines
6c differ from each other, wherein the first branch line 6c1 is longest, the first
branch line 6c2 is second longest, the first branch line 6c3 is third longest, the
first branch line 6c4 is fourth longest and the first branch line 6c5 is shortest.
[0071] A distance between the adjacent first branch lines 6c along the first one of the
above two sides is longer than a distance between adjacent parts of the wire material
of the first drive coil 6 before the wire material forming the first differential
coil 6 is branched off into the five first branch lines 6c. For example, a distance
d between the first branch lines 6c1 and 6c2 is longer than a distance D between the
adjacent parts of the wire material of the first differential coil 6. By making the
distance between the adjacent first branch lines 6c relatively longer, the amounts
of magnetic fluxes passing along the five first branch lines 6c can be made largely
different when the first drive coil 4 is driven.
[0072] When the first drive coil 4 is driven, the amount of magnetic flux passing along
the first branch line 6c is influenced by the length of a part of the first branch
line 6c extending along the outermost turn of the first drive coil 4 and a distance
between the outermost turn of the first drive coil 4 and the first branch line 6c.
A small amount of magnetic flux passes along the first branch line 6c if the length
of the part of the first branch line 6c extending along the outermost turn of the
first drive coil 4 is short, and a large amount of magnetic flux passes along the
first branch line 6c if the length of the part of the first branch line 6c extending
along the outermost turn of the first drive coil 4 is long. Further, a small amount
of magnetic flux passes along the first branch line 6c if the distance between the
outermost turn of the first drive coil 4 and the first branch line 6c is long, and
a large amount of magnetic flux passes along the first branch line 6c if the distance
is short.
[0073] For example, it is assumed that annular magnetic flux lines ML1, ML2, ML3 and ML4
are generated as shown in FIG. 15 when the first drive coil 4 is driven. The magnetic
flux lines ML3 and ML4 form concentric circles. The first branch line 6c1 passes through
the insides of all the magnetic flux lines ML1 to ML4. However, the first branch line
6c2 passes through the insides of the magnetic flux lines ML2, ML4, but does not pass
through the insides of the magnetic flux lines ML1, ML3. Thus, the amount of magnetic
flux passing along the first branch line 6c1 is more than the amount of magnetic flux
passing along the first branch line 6c2.
[0074] Accordingly, when the first drive coil 4 is driven, the following relationship of
the amount of magnetic flux holds: amount of magnetic flux passing along the first
branch line 6c1 > amount of magnetic flux passing along the first branch line 6c2
> amount of magnetic flux passing along the first branch line 6c3 > amount of magnetic
flux passing along the first branch line 6c4 > amount of magnetic flux passing along
the first branch line 6c5. For the same reason, when the second drive coil 5 is driven,
the following relationship of the amount of magnetic flux holds: amount of magnetic
flux passing along the second branch line 7c1 > amount of magnetic flux passing along
the second branch line 7c2 > amount of magnetic flux passing along the second branch
line 7c3 > amount of magnetic flux passing along the second branch line 7c4 > amount
of magnetic flux passing along the second branch line 7c5.
[0075] The first branch line 6c1 and the second branch line 7c1 have substantially the same
length and are facing each other. Similarly, the first branch line 6c2 and the second
branch line 7c2 have substantially the same length and are facing each other. The
first branch line 6c3 and the second branch line 7c3 have substantially the same length
and are facing each other. The first branch line 6c4 and the second branch line 7c4
have substantially the same length and are facing each other. The first branch line
6c5 and the second branch line 7c5 have substantially the same length and are facing
each other.
[0076] The first branch lines 6c and the second branch lines 7c are used for the zero adjustment
of the differential transformer of the magnetic sensor 3. This is described with reference
to FIGS. 6 and 10. As described above, the second drive coil 5 and the second differential
coil 7 are sterically intersected so that the wire material forming the second drive
coil 5 and that forming the second differential coil 7 do not come into contact. Thus,
the pattern of the second differential coil 7 arranged in the second outer area 43
cannot be made symmetrical with the pattern of the first differential coil 6 arranged
in the first outer area 33. As a result, the electromotive force V1 generated in the
first differential coil 6 and the electromotive force V2 generated in the second differential
coil 7 differ.
[0077] The first branch line 6c1 and the second branch line 7c1 are set as references. If
the electromotive force V1 generated in the first differential coil 6 is larger than
the electromotive force V2 generated in the second differential coil 7 in a state
where no magnetic substance (e.g. magnetic toner) is present near the magnetic sensor
3, any one of the first branch lines 6c2 to 6c5 is selected instead of the first branch
line 6c1 to make the electromagnetic force V1 smaller. The first branch line 6c5 can
make the electromagnetic force V1 smallest, then the first branch line 6c4, then the
first branch line 6c3 and then the first branch line 6c2.
[0078] On the other hand, if the electromotive force V1 is smaller than the electromotive
force V2 in a state where no magnetic substance e.g. magnetic toner is present near
the magnetic sensor 3, any one of the second branch lines 7c2 to 7c5 is selected instead
of the second branch line 7c1 to make the electromagnetic force V2 smaller. The second
branch line 7c5 can make the electromagnetic force V2 smallest, then the second branch
line 7c4, then the second branch line 7c3 and then the second branch line 7c2.
[0079] Next, the first selector unit 15 (FIG. 3) for selecting any one of the five first
branch lines 6c is described. With reference to FIG. 6, an end part of the first branch
line 6c1 is arranged at the position P1 and functions as the terminal 6d1. An end
part of the first branch line 6c2 is arranged at the position P2 and functions as
the terminal 6d2. An end part of the first branch line 6c3 is arranged at the position
P3 and functions as the terminal 6d3. An end part of the first branch line 6c4 is
arranged at the position P4 and functions as the terminal 6d4. An end part of the
first branch line 6c5 is arranged at the position P5 and functions as the terminal
6d5.
[0080] A first wiring 8 connected to the amplifier circuit 12 (FIG. 3) is arranged on the
first surface 31. The first wiring 8 is connectable to the five first branch lines
6c. The first wiring 8 includes a terminal 8a1 used for connection to the first branch
line 6c1, a terminal 8a2 used for connection to the first branch line 6c2, a terminal
8a3 used for connection to the first branch line 6c3, a terminal 8a4 used for connection
to the first branch line 6c4 and a terminal 8a5 used for connection to the first branch
line 6c5.
[0081] Any one of the five first branch lines 6c is connected to the first wiring 8 via
the resistor 13 described with reference to FIG. 3. This is described using FIGS.
6 and 16. FIG. 16 is a perspective view showing the substrate 21 near the selector
unit area 34 shown in FIG. 4. For example, if the resistor 13 is arranged at the position
P1 to connect the terminals 6d1 and 8a1, the first branch line 6c1 is connected to
the first wiring 8. That is, the first branch line 6c1 can be selected. The first
selector unit 15 is formed by the terminals 6d1, 8a1 at the position P1, the terminals
6d2, 8a2 at the position P2, the terminals 6d3, 8a3 at the position P3, the terminals
6d4, 8a4 at the position P4, the terminals 6d5, 8a5 at the position P5 and the resistor
13. The first selector unit 15 is used for the zero adjustment of the differential
transformer of the magnetic sensor 3 and can select any one of the five first branch
lines 6c.
[0082] The second selector unit 16 (FIG. 3) for selecting any one of the five second branch
lines 7c is described. With reference to FIG. 10, an end part of the second branch
line 7c1 functions as a terminal 7e1. An end part of the second branch line 7c2 functions
as a terminal 7e2. An end part of the second branch line 7c3 functions as a terminal
7e3. An end part of the second branch line 7c4 functions as a terminal 7e4. An end
part of the second branch line 7c5 functions as a terminal 7e5.
[0083] A second wiring 9 connected to the amplifier circuit 12 (FIG. 3) is arranged on the
second surface 41. The second wiring 9 is connectable to the five second branch lines
7c. The second wiring 9 includes a terminal 9a1 used for connection to the second
branch line 7c1, a terminal 9a2 used for connection to the second branch line 7c2,
a terminal 9a3 used for connection to the second branch line 7c3, a terminal 9a4 used
for connection to the second branch line 7c4 and a terminal 9a5 used for connection
to the second branch line 7c5.
[0084] The second branch line 7c and the second wiring 9 are connected at any one of the
positions P6, P7, P8, P9 and P10 on the first surface 31 shown in FIG. 6. With reference
to FIGS. 6 and 16, the position P6 is adjacent to the position P1 and terminals 7f1
and 9b1 are arranged there. The terminal 7f1 and the terminal 7e1 of the second branch
line 7c1 are connected by a fourth connecting member 54a. The terminal 9b1 and the
terminal 9a1 of the second wiring 9 are connected by a fourth connecting member 54b.
[0085] The position P7 is adjacent to the position P2 and terminals 7f2 and 9b2 are arranged
there. The terminal 7f2 and the terminal 7e2 of the second branch line 7c2 are connected
by a fourth connecting member 54c. The terminal 9b2 and the terminal 9a2 of the second
wiring 9 are connected by a fourth connecting member 54d.
[0086] The position P8 is adjacent to the position P3 and terminals 7f3 and 9b3 are arranged
there. The terminal 7f3 and the terminal 7e3 of the second branch line 7c3 are connected
by a fourth connecting member 54e. The terminal 9b3 and the terminal 9a3 of the second
wiring 9 are connected by a fourth connecting member 54f.
[0087] The position P9 is adjacent to the position P4 and terminals 7f4 and 9b4 are arranged
there. The terminal 7f4 and the terminal 7e4 of the second branch line 7c4 are connected
by a fourth connecting member 54g. The terminal 9b4 and the terminal 9a4 of the second
wiring 9 are connected by a fourth connecting member 54h.
[0088] The position P10 is adjacent to the position P5 and terminals 7f5 and 9b5 are arranged
there. The terminal 7f5 and the terminal 7e5 of the second branch line 7c5 are connected
by a fourth connecting member 54i. The terminal 9b5 and the terminal 9a5 of the second
wiring 9 are connected by a fourth connecting member 54j.
[0089] The fourth connecting members 54a to 54j are embedded in through holes (not shown)
formed in the substrate 21.
[0090] Any one of the five second branch lines 7c is connected to the second wiring 9 via
the capacitor 14 described with reference to FIG. 3. With reference to FIG. 16, for
example, if the capacitor 14 is arranged at the position P6 to connect the terminals
7f1 and 9b1, the second branch line 7c1 is connected to the second wiring 9. The second
selector unit 16 is formed by the terminals 7f1, 9b1 at the position P6, the terminals
7f2, 9b2 at the position P7, the terminals 7f3, 9b3 at the position P8, the terminals
7f4, 9b4 at the position P9, the terminals 7f5, 9b5 at the position P10 and the capacitor
14. The second selector unit 16 is used for the zero adjustment of the differential
transformer of the magnetic sensor 3 and can select any one of the five second branch
lines 7c.
[0091] Main effects of this embodiment are described.
[0092] With reference to FIGS. 7, 8, 11 and 12, the first drive coil 4 and the first differential
coil 6 are wound in the same direction and the second drive coil 5 and the second
differential coil 7 are wound in the opposite directions in the differential transformer
including the first drive coil 4, the first differential coil 6, the second drive
coil 5 and the second differential coil 7. Since the wire material forming the first
drive coil 4 and that forming the first differential coil 6 are alternately arranged
in the first outer area 33 (FIG. 4) in this embodiment, magnetic coupling between
these coils can be increased. Further, since the wire material forming the second
drive coil 5 and that forming the second differential coil 7 are alternately arranged
in the second outer area 43 (FIG. 5), magnetic coupling between these coils can be
increased.
[0093] Since the second drive coil 5 and the second differential coil 7 are wound in the
opposite directions, the intersection of the wire material forming the second drive
coil 5 and that forming the second differential coil 7 is unavoidable. If the second
drive coil 5 and the second differential coil 7 come into contact, a short circuit
occurs between these coils. Accordingly, in this embodiment, the wire material forming
the second drive coil 5 and that forming the differential coil 7 are sterically intersected
using the connection patterns 10a to 10g (FIG. 9) and the third connecting members
(third connecting members 53a 53b connected with the connection pattern 10a and third
connecting members 53c, 53d connected with the connection pattern 10b are shown in
FIG. 13) . This prevents the contact of the second drive coil 5 and the second differential
coil 7 while causing the wire material forming the second drive coil 5 and that forming
the second differential coil 7 to intersect.
[0094] In this embodiment, as shown in FIGS. 6 and 10, the first drive coil 4 and the first
differential coil 6 are arranged on the first surface 31 of the substrate 21 and the
second drive coil 5 and the second differential coil 7 are arranged on the second
surface 41 on the side opposite to the first surface 31. Since the first drive coil
4, the first differential coil 6, the second drive coil 5 and the second differential
coil 7 are arranged on one substrate 21 in this way, the magnetic sensor 3 can be
miniaturized.
[0095] As described above, according to this embodiment, magnetic coupling between the first
drive coil 4 and the first differential coil 6 and that between the second drive coil
5 and the second differential coil 7 can be increased and the magnetic sensor 3 can
be miniaturized. This can realize a highly accurate differential transformer type
magnetic sensor while realizing a configuration that the planar coils arranged on
the substrate 21 are formed by the drive coils (first drive coil 4, second drive coil
5) and the differential coils (first differential coil 6, second differential coil
7). Further, since the first drive coil 4, the first differential coil 6, the second
drive coil 5 and the second differential coil 7 are arranged not on a plurality of
layers of substrates, but on one layer of the substrate 21, the cost of the magnetic
sensor 3 can be reduced.
[0096] Note that the steric intersection is realized by constituting parts of the second
differential coil 7 by the connection patterns 10a to 10g (FIG. 9) in this embodiment.
Taking the connection pattern 10a as an example, the wire material forming the second
differential coil 7 and that forming the second drive coil 5 are sterically intersected
by connecting the connection pattern 10a to the wire material forming the second differential
coil 7 (dotted line) by the third connecting members 53a, 53b as shown in FIG. 13.
However, the steric intersection may be realized by constituting parts of the second
drive coil 5 (chain double-dashed line) by the connection patterns 10a to 10g. Specifically,
taking the connection pattern 10a as an example, the wire material forming the second
differential coil 7 and that forming the second drive coil 5 are sterically intersected
by connecting the connection pattern 10a to the wire material forming the second drive
coil 5 by the third connecting members 53a, 53b.
[0097] Although the first differential coil 6 is the reference coil and the second differential
coil 7 is the detection coil in this embodiment, the first differential coil 6 may
be the detection coil and the second differential coil 7 may be the reference coil.
[0098] According to this embodiment, as shown in FIG. 6, the five first branch lines 6c1
to 6c5 are so arranged that the amounts of magnetic fluxes passing along the respective
first branch lines 6c1 to 6c5 differ when the first drive coil 4 is driven. Thus,
the magnitude of the electromagnetic force V1 generated in the first differential
coil 6 can be adjusted by selecting any one of the five first branch lines 6c1 to
6c5 by the first selector unit 15 (FIG. 3) . Similarly, as shown in FIG. 10, the five
second branch lines 7c1 to 7c5 are so arranged that the amounts of magnetic fluxes
passing along the respective second branch lines 7c1 to 7c5 differ when the second
drive coil 5 is driven. Thus, the magnitude of the electromagnetic force V2 generated
in the second differential coil 7 can be adjusted by selecting any one of the five
second branch lines 7c1 to 7c5 by the second selector unit 16 (FIG. 3). By the above,
according to this embodiment, the zero adjustment of the differential transformer
of the magnetic sensor 3 can be made on the substrate 21 when the planar coils arranged
on the substrate 21 are formed by the drive coils and the differential coils. This
can realize a highly accurate differential transformer type magnetic sensor while
realizing the configuration that the planar coils arranged on the substrate 21 are
formed by the drive coils (first drive coil 4, second drive coil 5) and the differential
coils (first differential coil 6, second differential coil 7).
[0099] Although both the first selector unit 15 and the second selector unit 16 are provided
in this embodiment, only either one of the first and second selector units 15, 16
may be provided. This is described, taking the first selector unit 15 as an example.
The second branch lines 7c1 to 7c5 shown in FIG. 10 are assumed to be one second branch
line 7c3. The first branch line 6c3 shown in FIG. 6 is set as a reference. If the
electromagnetic force V1 generated in the first differential coil 6 is larger than
the electromagnetic force V2 generated in the second differential coil 7, either one
of the first branch lines 6c4 and 6c5 is selected instead of the first branch line
6c3 to make the electromagnetic force V1 smaller. Contrary to this, if the electromagnetic
force V1 is smaller than the electromagnetic force V2, either one of the first branch
lines 6c1 and 6c2 is selected instead of the first branch line 6c3 to make the electromagnetic
force V1 larger.
[0100] With reference to FIG. 16, according to this embodiment, the resistor 13 used to
set an amplification factor at which the differential voltage V0 is amplified in the
amplifier circuit 12 is used as a connecting member for connection between any one
of the five first branch lines 6c1 to 6c5 and the first wiring 8. The capacitor 14
for cutting a direct-current component of the differential voltage V0 is used as a
connecting member for connection between any one of the five second branch lines 7c1
to 7c5 and the second wiring 9. Accordingly, it is not necessary to provide these
connecting members anew. Note that the capacitor 14 may be used as the connecting
member for connection between any one of the five first branch lines 6c1 to 6c5 and
the first wiring 8 and the resistor 13 may be used as the connecting member for connection
between any one of the five second branch lines 7c1 to 7c5 and the second wiring 9.
Further, zero ohm resistors mountable on the surface of the substrate 21 can be used
instead of the resistor 13 and the capacitor 14 . Further, mechanical or electronic
switches can also be used instead of the resistor 13, the capacitor 14 or the zero
ohm resistors. In this case, any one of the five first branch lines 6c1 to 6c5 and
the first wiring 8 can be made connectable by a first switch and any one of the five
second branch lines 7c1 to 7c5 and the second wiring 9 can be made connectable by
a second switch.
[0101] With reference to FIGS. 4 and 5, according to this embodiment, the first and second
selector units 15, 16 are arranged on the first surface 31 on which the first differential
coil 6 (reference coil) is arranged. Thus, no projections such as the first and second
selector units 15, 16 are arranged on the second surface 41 (detection coil surface)
on which the second differential coil 7 (detection coil) is arranged, wherefore a
distance between the second surface 41 and the magnetic substance can be shortened.
Hence, a highly accurate differential transformer type magnetic sensor can be realized.
[0102] Note that if a combination of the first branch line and the second branch line used
for the zero adjustment out of the five first branch lines 6c1 to 6c5 and the five
second branch lines 7c1 to 7c5 is already known, unnecessary branch lines may be omitted.
For example, if it is already known that the zero adjustment can be made by a combination
of the first branch line 6c2 and the second branch line 7c5, the first branch lines
6c1, 6c3 to 6c5 and the second branch lines 7c1 to 7c4 may not be provided. This configuration
can be so expressed that an arrangement is made such that the amount of magnetic flux
passing along the wire material (first branch line 6c2) forming the outermost turn
of the first differential coil 6 and the amount of magnetic flux passing along the
wire material (second branch line 7c5) forming the outermost turn of the second differential
coil 7 differ.
[0103] With reference to FIGS. 4 and 5, in this embodiment, the first differential coil
6 is arranged in the first inner and outer areas 32, 33 and the second differential
coil 7 is arranged in the second inner and outer areas 42, 43. However, the first
differential coil 6 may not be necessarily in the first inner area 32 if there is
no problem in the sensitivity of the first differential coil 6. Similarly, the second
differential coil 7 may not be necessarily in the second inner area 42 if there is
no problem in the sensitivity of the first differential coil 7.
[0104] Although this embodiment is described, taking the substrate 21 including one insulating
layer as an example, the present disclosure can be applied also to a substrate including
a plurality of insulating layers. This is described as a modification of this embodiment.
FIG. 17 is a sectional view of a substrate 61 formed with a differential transformer
type magnetic sensor 60 according to the modification of the present disclosure. The
substrate 61 includes three insulating layers, i.e. an insulating layer 62, an insulating
layer 63 located below the insulating layer 62 and an insulating layer 64 located
above the insulating layer 62.
[0105] A first differential coil 65 in the form of a planar coil is arranged on the upper
surface of the insulating layer 64. The first differential coil 65 includes a plurality
of first branch lines formed by branching a wire material forming the outermost turn
of the first differential coil 65 similarly to the first differential coil 6 shown
in FIG. 8.
[0106] A first drive coil 66 in the form of a planar coil is arranged between the lower
surface of the insulating layer 64 and the upper surface of the insulating layer 63.
A second drive coil 67 in the form of a planar coil is arranged between the lower
surface of the insulating layer 63 and the upper surface of the insulating layer 62.
One end of the first drive coil 66 and one end of the second drive coil 67 are connected
using a connecting member 68 so that a magnetic flux generated in the first drive
coil 66 and that generated in the second drive coil 67 flow in the same direction
when a high-frequency current flows in the first and second drive coils 66, 67. The
connecting member 68 is embedded in a through hole formed in the insulating layer
63.
[0107] A second differential coil 69 in the form of a planar coil is arranged on the lower
surface of the insulating layer 62. The second differential coil 69 includes a plurality
of second branch lines formed by branching a wire material forming the outermost turn
of the second differential coil 69 similarly to the second differential coil 7 shown
in FIG. 12.
[0108] One end of the first differential coil 65 and one end of the second differential
coil 69 are connected using a connecting member 70 so that a magnetic flux generated
in the first differential coil 65 and that generated in the second differential coil
69 flow in opposite directions when an induction current flows in the first and second
differential coils 65, 69. The connecting member 70 is embedded in a through hole
penetrating through the insulating layers 62, 63 and 64.
[0109] A first selector unit 15 (FIG. 3) used for a zero adjustment of a differential transformer
and capable of selecting any one of the plurality of first branch lines is arranged
on the upper surface of the insulating layer 64. A second selector unit 16 (FIG. 3)
used for the zero adjustment of the differential transformer and capable of selecting
any one of the plurality of second branch lines is arranged on the lower surface of
the insulating layer 62. Note that the second selector unit 16 may be arranged on
the upper surface of the insulating layer 64.
[0110] In this embodiment, the first drive coil 4 corresponds to the first differential
coil 6 and the second drive coil 5 corresponds to the second differential coil 7.
However, the drive coil and the differential coil may not correspond one-to-one. For
example, in the case of two insulating layers, a first differential coil may be arranged
on the upper surface of a first insulating layer, a drive coil may be arranged between
the lower surface of the first insulating layer and the upper surface of a second
insulating layer, and a second differential coil may be arranged on the lower surface
of the second insulating layer.
[0111] Although the differential transformer type magnetic sensor 3 is exemplarily described
as the sensor for detecting the toner/carrier mixing ratio (toner remaining amount
in the one-component development method) of the image forming apparatus 1 in the above
embodiment and its modification, the use of the differential transformer type magnetic
sensor according to the present disclosure is not limited to these.
[0112] Although the present disclosure has been fully described by way of example with reference
to the accompanying drawings, it is to be understood that various changes and modifications
will be apparent to those skilled in the art. Therefore, unless otherwise such changes
and modifications depart from the scope of the present disclosure hereinafter defined,
they should be construed as being included therein.
1. Ein Magnetsensor vom Typ Differenzialtransformator, der Folgendes umfasst:
ein Substrat (21), das eine erste Oberfläche (31) aufweist und eine zweite Oberfläche
(41) aufweist, die an einer zur ersten Oberfläche (31) gegenüberliegenden Seite liegt;
eine erste Antriebsspule (4), die eine auf der ersten Oberfläche (31) angeordnete
planare Spule beinhaltet;
eine erste differenzielle Spule (6), die eine planare Spule beinhaltet, die in derselben
Richtung wie die erste Antriebsspule (4) gewickelt ist und auf der ersten Oberfläche
(31) angeordnet ist und konfiguriert ist, um eine elektromotorische Kraft zu erzeugen,
wenn die erste Antriebsspule (4) angetrieben wird;
eine zweite Antriebsspule (5), die eine planare Spule beinhaltet, die in einer Richtung
gewickelt ist, die, bei Betrachtung von der Seite der ersten Oberfläche (31), der
ersten Antriebsspule (4) entgegengesetzt ist und die auf der zweiten Oberfläche (41)
angeordnet ist;
ein erstes Verbindungsglied (51), das das Substrat (21) durchdringt und das ein Ende
der ersten Antriebsspule (4) und ein Ende der zweiten Antriebsspule (5) verbindet;
eine zweite differenzielle Spule (7), die eine planare Spule beinhaltet, die in einer
Richtung gewickelt ist, die der zweiten Antriebsspule (5) entgegengesetzt ist und
die auf der zweiten Oberfläche (41) angeordnet ist und konfiguriert ist, um eine elektromotorische
Kraft zu erzeugen, wenn die zweite Antriebsspule (5) angetrieben wird;
ein zweites Verbindungsglied (52), das das Substrat (21) durchdringt und das ein Ende
der ersten differenziellen Spule (6) und ein Ende der zweiten differenziellen Spule
(7) verbindet;
ein drittes Verbindungsglied (53a-53d), das gebildet wird, um das Substrat (21) zu
durchdringen; und
ein Anschlussraster (10a-10g), das auf der ersten Oberfläche (31) angeordnet ist und
das einen Teil der zweiten Antriebsspule (5) oder einen Teil der zweiten differenziellen
Spule (7) konstituiert;
wobei
ein Drahtmaterial, das die erste Antriebsspule (4) bildet, und dasjenige, das die
erste differenzielle Spule (6) bildet abwechselnd auf der ersten Oberfläche (31) angeordnet
wird;
ein Drahtmaterial, das die zweite Antriebsspule (5) bildet, und dasjenige, das die
zweite differenzielle Spule (7) bildet abwechselnd auf der zweiten Oberfläche (41)
angeordnet wird; und wobei
das Anschlussraster durch das dritte Verbindungsglied mit dem Drahtmaterial verbunden
ist, das die zweite Antriebsspule (5) bildet, oder dasjenige, das die zweite differenzielle
Spule (7) bildet, wobei das Drahtmaterial, das die zweite differenzielle Spule (7)
bildet und dasjenige, das die zweite Antriebsspule (5) bildet sich sterisch schneiden,
wobei der Magnetsensor vom Typ Differenzialtransformator des Weiteren mindestens einen
der Folgenden umfasst: eine erste Auswahleinheit (15) und eine zweite Auswahleinheit
(16);
wobei:
die erste Auswahleinheit (15) zu einer Nullpunkteinstellung eines Differenzialtransformators
angepasst ist, der aus der ersten Antriebsspule (4), der zweiten Antriebsspule (5),
der ersten differenziellen Spule (6) und der zweiten differenziellen Spule (7) gebildet
wird; und
die zweite Auswahleinheit (16) zur Nullpunkteinstellung des Differenzialtransformators
angepasst ist;
dadurch gekennzeichnet, dass
die erste differenzielle Spule (6) eine Vielzahl an ersten Abzweigleitungen (6c1 -
6c5) beinhaltet, die durch Verzweigen eines Drahtmaterials gebildet werden, das die
äußerste Windung der ersten differenziellen Spule (6) bildet;
die zweite differenzielle Spule (7) eine Vielzahl an zweiten Abzweigleitungen (7c1
- 7c5) beinhaltet, die durch Verzweigen eines Drahtmaterials gebildet werden, das
die äußerste Windung der zweiten differenziellen Spule (7) bildet;
die Vielzahl an ersten Abzweigleitungen (6c1 - 6c5) derart angeordnet sind, dass die
Magnetflussmenge bzw. Magnetflussdichte die entlang der Vielzahl an entsprechenden
ersten Abzweigleitungen (6c1 - 6c5) fließt, unterschiedlich ist, wenn die erste Antriebsspule
(4) angesteuert wird;
die Vielzahl an zweiten Abzweigleitungen (7c1 - 7c5) derart angeordnet sind, dass
die Magnetflussmenge bzw. Magnetflussdichte die entlang der Vielzahl an entsprechenden
zweiten Abzweigleitungen (7c1 - 7c5) fließt, unterschiedlich ist, wenn die zweite
Antriebsspule (5) angesteuert wird;
die erste Auswahleinheit (15) in der Lage ist, irgendeine aus der Vielzahl an ersten
Abzweigleitungen (6c1 - 6c5) auszuwählen, und auf dem Substrat (21) angeordnet ist;
und
die zweite Auswahleinheit (16) in der Lage ist, irgendeine aus der Vielzahl an zweiten
Abzweigleitungen (7c1 - 7c5) auszuwählen, und auf dem Substrat (21) angeordnet ist.
2. Ein Magnetsensor vom Typ Differenzialtransformator nach Anspruch 1, wobei:
Längen innerhalb der Vielzahl an ersten Abzweigleitungen (6c1 - 6c5) untereinander
unterschiedlich sind; und
Längen innerhalb der Vielzahl an zweiten Abzweigleitungen (7c1 - 7c5) untereinander
unterschiedlich sind.
3. Ein Magnetsensor vom Typ Differenzialtransformator nach Anspruch 1 oder 2, wobei:
ein Abstand zwischen benachbarten unter den ersten Abzweigleitungen (6c1 - 6c5) größer
ist als ein Abstand zwischen benachbarten Teilen eines Drahtmaterials, das die erste
differenzielle Spule (6) bildet, bevor das die erste differenzielle Spule (6) bildende
Drahtmaterial zu der Vielzahl an ersten Abzweigleitungen (6c1 - 6c5) abgezweigt wird;
und
ein Abstand zwischen benachbarten unter den zweiten Abzweigleitungen (7c1 - 7c5) größer
ist als ein Abstand zwischen benachbarten Teilen eines Drahtmaterials, das die zweite
differenzielle Spule (7) bildet, bevor das die zweite differenzielle Spule (7) bildende
Drahtmaterial zu der Vielzahl an zweiten Abzweigleitungen (7c1 - 7c5) abgezweigt wird.
4. Ein Magnetsensor vom Typ Differenzialtransformator nach irgendeinem der vorhergehenden
Ansprüche, der des Weiteren Folgendes umfasst:
eine erste Verdrahtung (8), die mit der Vielzahl an ersten Abzweigleitungen (6c1 -
6c5) verbindbar ist;
eine zweite Verdrahtung (9), die mit der Vielzahl an zweiten Abzweigleitungen (7c1
- 7c5) verbindbar ist;
einen Verstärker (12) mit dem die erste Verdrahtung (8) und die zweite Verdrahtung
(9) verbunden sind;
einen Widerstand (13), der verwendet wird, um einen Verstärkungsfaktor zu setzen,
um den eine Differenzialspannung zwischen der elektromotorischen Kraft, die in der
ersten differenziellen Spule (6) generiert wird, und derjenigen, die in der zweiten
differenziellen Spule (7) generiert wird, im Verstärker (12) verstärkt wird; und
einen Kondensator (14), um einen Gleichstromanteil der Differenzialspannung zu entfernen;
wobei
einer der Folgenden: der Widerstand (13) und der Kondensator (14) verwendet wird,
um irgendeinen aus der Vielzahl an ersten Abzweigleitungen (6c1 - 6c5) mit der ersten
Verdrahtung (8) in der ersten Auswahleinheit (15) zu verbinden, wobei irgendeine aus
der Vielzahl an ersten Abzweigleitungen (6c1 - 6c5) ausgewählt ist; und
der andere unter den Folgenden: der Widerstand (13) und der Kondensator (14) verwendet
wird, um irgendeinen aus der Vielzahl an zweiten Abzweigleitungen (7c1 - 7c5) mit
der zweiten Verdrahtung (9) in der zweiten Auswahleinheit (16) zu verbinden, wobei
irgendeine aus der Vielzahl an zweiten Abzweigleitungen (7c1 - 7c5) ausgewählt ist.
5. Ein Magnetsensor vom Typ Differenzialtransformator nach irgendeinem der vorhergehenden
Ansprüche, wobei:
die erste differenzielle Spule (6) die Funktion einer Referenzspule hat;
die zweite differenzielle Spule (7) die Funktion einer Detektionsspule hat; und
die erste (15) und die zweite Auswahleinheit (16) auf der ersten Oberfläche (31) angeordnet
sind.